New CAT. New aftermarket or used Porsche OEM?

[oc-boxster]

I would have a Porsche mechanic verify with codes that it is in fact one of the cats, you have 2 how do you know which one it is? They also have heat shields that come loose that cause noise sometimes too. You could just have some type of a bad exhaust leak somewhere. If one of the cats is bad you will get a check engine light on the dash. Find out exactly what's wrong before you just start replacing parts.